Pitaksakulrat, O. et al. (2017) Preliminary genetic evidence of two different populations of Opisthorchis viverrini

31 Opisthorchis viverrini is a major public health concern in Southeast Asia. Various reports have suggested that 32 this parasite may represent a species complex, with genetic structure in the region perhaps being dictated by 33 geographical factors and different species of intermediate hosts. We used four microsatellite loci to analyze O. 34 viverrini adult worms originating from six species of cyprinid fish in Thailand and Lao PDR. Two distinct O. 35 viverrini populations were observed. In Ban Phai, Thailand, only one subgroup occurred, hosted by two 36 different fish species. Both subgroups occurred in fish from That Luang, Lao PDR, but were represented to very 37 different degrees among the fish hosts there. Our data suggest that, although geographical separation is more 38 important than fish host specificity in influencing genetic structure, it is possible that two species of 39 Opisthorchis, with little interbreeding, are present near Vientiane in Lao PDR. 40 41